**3. Physio-chemical properties of sugar bagasse**

#### **3.1. Fibers**

for first generation ethanol requires high feedstock production which will lead to food against fuel concerns. The second-generation biofuels becomes the favorite choice since it depends on non-food bio resources such as lignocellulosic. The lignocellulosic materials are relatively inexpensive and available in large quantities. One of the most well-known lignocellulosic

According to the available literature about 640–660 Mton of sugarcane could generate a total of 28,500 million liters of alcohol, with the aim of producing 45.4% of sugar and 54.6% of alcohol. This would apparently produce 160 Mton of sugarcane bagasse [3]. Generally sugar cane bagasse consists of cellulose (41.0–55.0 wt%), hemicellulose (20.0–27.5 wt%), lignin (18.0–26.3 wt%) and others (~7.0 wt%) attributed to inorganic materials [3–5]. Sugarcane bagasse can be employed for other applications that include extraction of all the constituents (cellulose, hemicellulose and lignin) [4, 5]. Furthermore the sugarcane bagasse ash could be used as raw material for obtaining new type of mortars and concretes [6]. In fact, it has also a

In this chapter we cover all the aspects related to the residues and/or left overs resulting from sugar extraction process. These residues can be used for various applications especially in polymer composite. The high mechanical strength of the sugar bagasse fibers as well as its constituents such as lignin, hemicellulose and cellulose can be added to polymeric matrices to produce multifunctional composite materials. The ashes from the burning of sugar bagasse as source of energy for sugar extraction and alcohol industry can also be used for polymer

**2. The production of sugarcane bagasse globally (producing countries)**

Sugarcane bagasse originates from Asia and can be found mostly in tropical and subtropical climates [1]. For instance, *Saccharum spontaneum* is endemic in the wild from eastern and northern Africa, through the Middle East, to India, China, Taiwan and Malaysia through the pacific to the New Guinea. Globally (mostly in Latin America and Asia), the production of sugarcane bagasse was approximately 1900 million metric in the past 5 years. Brazil is by far the world's largest sugarcane producer with around 740 million ton cane crushed in the 2010/2011 harvest season, which is about 43% of the global production. **Table 1** summarizes the sugarcane crop production in selective countries between years 2009 and 2013. Brazil is also the largest exporter of ethanol, and it is widely expected that Brazil has a large potential for growth in the next decades. At the sugar mills, bagasse has been used to fuel the boilers that supply the thermal and electrical power needed for the internal processes of the sugar

Columbia has been producing sugarcane and palm oil since the early 1900s. Most of Colombia sugarcane bagasse plantations are situated around the Cauca River Valley, and grow the whole with the potential to produce 950,000 ld−1 of ethanol from sugarcane juice. There are approximately more than 20,000 registered sugarcane growers regions in South Africa which include the province of KwaZulu-Natal, Mpumalanga and Eastern Cape. The majority of sugarcane

materials for second-generation ethanol production is sugarcane bagasse [1, 2].

potential to partially replace Portland cement [7].

reinforcement.

226 Sugarcane - Technology and Research

mills.

Sugarcane bagasse is a fibrous material obtained as a residue from the sugarcane after crushing to extract the juice. Its stalk is composed of two components *viz.* outer rind and inner pith [11, 12]. The rind consists of strong fibrous structure protecting the inner soft spongy structured material (pith). It contained long finer fibers arranged randomly throughout the stem bound together by lignin and hemicellulose, while the inner component contains small fibers with major part being sucrose. Chemically, sugarcane bagasse composed of cellulose, hemicellulose and lignin [13]. The content of these constituents may vary depending on the growth region and conditions. About 40–50% of dried sugarcane bagasse is cellulose with 25–35% is hemicellulose and 17–20% lignin with some wax 0.8% and ash 2.3% [12, 13]. All these components have similar structure as the constituents of every natural lignocellulosic fibers and, the only difference is their content. In the next subsection only part of sugarcane bagasse and products that can be used as reinforcing fillers of various polymer matrices will be discussed. Moreover, carbonized sugar bagasse can be prepared by alkali treatment followed by burning in the furnace at higher temperature (>500°C) to produce ashes as shown in **Figure 1** [14]. These particles also serve as the most potential reinforcement for various polymeric materials. They appear solid in nature with irregular finer shapes; and it composed mainly of SiO<sup>2</sup> , AlO<sup>3</sup> , MgO, and Fe<sup>2</sup> O3 .

the unfriendly disposal methods such as mixing the ash with water and discarding it into the open field and/or using these ashes as fertilizers. The ashes are composed of highly crystalline

constituents varies with crystalline silica being the major constituent (60 to above 80%). The variation is as a result of the growing conditions of the sugarcane bagasse as well as other factors such as soil type, fertilization methods, and soil management. Moreover, the physical and chemical compositions are directly influenced by combustion processes such as combustion temperature and time, cooling duration, ash collection methods and grinding conditions [27]. It is noteworthy mentioning that despite these variations and the reasons given from each study, it can be concluded that these variations comes due to the fact that sugar bagasse is a natural material. The chemical composition can vary as tabulated in **Table 2**. These properties plays major role on the performance of the product manufactured from these ashes. Therefore one of the prerequisite before implementing sugarcane bagasse ashes is to characterize their composition using techniques such as XRD (for crystallography) and EDX (for chemical analysis) as well as to measure their size and/morphology using microscopic techniques such as SEM and other. Loss on ignition (LOI) is also considered to measure the organic matter in the sample or the amount of carbon which reflects extends of ashes combustion. The higher LOI indicates that the amount of unburnt carbon in the ash. The crystalline phase of mullite depends on the ratio of Si/Al of the material. At low Al content the tetragonal structure is obtained which changes to orthorhombic structure at higher Al content. Its nucleation can be accelerated by adding additives, flux or mineralizer. The degree of crystallinity for silica is also dependent on the combustion temperature. If higher temperatures are used during combustion, the more crystalline silica is obtained and for low combustion temperatures the opposite prevails. These changes in combustion affect the specific area and the morphology of the resulting ashes. As mentioned earlier the carbon content can be controlled by these

), and mullite (3Al<sup>2</sup>

), potassium carbonate (K<sup>2</sup>

O3 ·2SiO<sup>2</sup> CO<sup>3</sup>

Sugarcane Bagasse and Cellulose Polymer Composites http://dx.doi.org/10.5772/intechopen.71497

), calcium phosphate

229

) [24]. The percentage of these

), cristobalite (SiO<sup>2</sup>

O3

phases *viz.* quartz (SiO<sup>2</sup>

O), hematite (Fe<sup>2</sup>

SiO<sup>2</sup> 60–86

O<sup>3</sup> 1–14

O<sup>3</sup> 1–14 TiO<sup>2</sup> 0.2–3 CaO 2–7 MgO 0.05–2 MnO 0.1–0.5

O 0.2–6

O<sup>5</sup> 0.5–3.5 SO<sup>3</sup> 0.2–2.5

O 0.01–0.1

O<sup>3</sup> 0.01–0.1

**Table 2.** Chemical composition of sugarcane bagasse ashes [24].

(Ca<sup>3</sup> (PO4 )2 ·H2

Al<sup>2</sup>

Fe2

K2

P2

Na<sup>2</sup>

Cr<sup>2</sup>

**Figure 1.** SEM images of (a) uncarbonized and (b) carbonized sugar bagasse [14].

#### *3.1.1. Cellulose*

Cellulose from sugarcane bagasse can be extracted by using either chemical or mechanical means [15–17]. In some cases both of these (chemical and mechanical) methods are used in order to control the size as well as to improve the purity of the resulting product. A combination of mechanical shearing (or sonication) and controlled acid hydrolysis (or combination of acids) are often used to isolate the cellulose. This kind of cellulose is also known in literature as microfibrillated cellulose (MFC) due to their size diameters ranging from few nanometer to few micrometers, while their length may be above a micron [15–18]. Depending on the time and acid concentration the lateral amorphous region of the MFC can be dissolved to obtain highly crystalline particles. This kind of cellulose particles are known in literature as cellulose nanocrystals (CNC), cellulose nanowhiskers (CNW), cellulose whiskers (CW), microcrystals, or cellulose nanoparticles. These particles have diameters ranges between 5 and 20 nm and the lengths from 20 nm to 1 micron. Tensile strength and/or modulus of these particles and the abundant availability of their source spurred much interest as replacement of engineered reinforcing fillers [19]. The presence of the hydroxyl groups on the surface of these particles offers the advantage for their functionalization [20, 21].

#### *3.1.2. Ashes*

Sugarcane industries produce large quantities of sugarcane bagasse (i.e., fibrous residue/left over after sugarcane stalks are crushed to extract their juice) annually which in turn is used in the plant for energy co-generation for sugar processing and/or alcohol production [22–26]. Consequently, the black solid waste produced is collected using a bag house filter as a byproduct known as sugarcane bagasse ashes. The collected by-product often consists of fine burnt and coarse unburnt or partially burnt particles. These ashes are non-biodegradable which causes environmental concerns considering their disposal. Some industries adopted the unfriendly disposal methods such as mixing the ash with water and discarding it into the open field and/or using these ashes as fertilizers. The ashes are composed of highly crystalline phases *viz.* quartz (SiO<sup>2</sup> ), cristobalite (SiO<sup>2</sup> ), potassium carbonate (K<sup>2</sup> CO<sup>3</sup> ), calcium phosphate (Ca<sup>3</sup> (PO4 )2 ·H2 O), hematite (Fe<sup>2</sup> O3 ), and mullite (3Al<sup>2</sup> O3 ·2SiO<sup>2</sup> ) [24]. The percentage of these constituents varies with crystalline silica being the major constituent (60 to above 80%). The variation is as a result of the growing conditions of the sugarcane bagasse as well as other factors such as soil type, fertilization methods, and soil management. Moreover, the physical and chemical compositions are directly influenced by combustion processes such as combustion temperature and time, cooling duration, ash collection methods and grinding conditions [27]. It is noteworthy mentioning that despite these variations and the reasons given from each study, it can be concluded that these variations comes due to the fact that sugar bagasse is a natural material. The chemical composition can vary as tabulated in **Table 2**. These properties plays major role on the performance of the product manufactured from these ashes. Therefore one of the prerequisite before implementing sugarcane bagasse ashes is to characterize their composition using techniques such as XRD (for crystallography) and EDX (for chemical analysis) as well as to measure their size and/morphology using microscopic techniques such as SEM and other. Loss on ignition (LOI) is also considered to measure the organic matter in the sample or the amount of carbon which reflects extends of ashes combustion. The higher LOI indicates that the amount of unburnt carbon in the ash. The crystalline phase of mullite depends on the ratio of Si/Al of the material. At low Al content the tetragonal structure is obtained which changes to orthorhombic structure at higher Al content. Its nucleation can be accelerated by adding additives, flux or mineralizer. The degree of crystallinity for silica is also dependent on the combustion temperature. If higher temperatures are used during combustion, the more crystalline silica is obtained and for low combustion temperatures the opposite prevails. These changes in combustion affect the specific area and the morphology of the resulting ashes. As mentioned earlier the carbon content can be controlled by these


**Table 2.** Chemical composition of sugarcane bagasse ashes [24].

*3.1.1. Cellulose*

228 Sugarcane - Technology and Research

*3.1.2. Ashes*

Cellulose from sugarcane bagasse can be extracted by using either chemical or mechanical means [15–17]. In some cases both of these (chemical and mechanical) methods are used in order to control the size as well as to improve the purity of the resulting product. A combination of mechanical shearing (or sonication) and controlled acid hydrolysis (or combination of acids) are often used to isolate the cellulose. This kind of cellulose is also known in literature as microfibrillated cellulose (MFC) due to their size diameters ranging from few nanometer to few micrometers, while their length may be above a micron [15–18]. Depending on the time and acid concentration the lateral amorphous region of the MFC can be dissolved to obtain highly crystalline particles. This kind of cellulose particles are known in literature as cellulose nanocrystals (CNC), cellulose nanowhiskers (CNW), cellulose whiskers (CW), microcrystals, or cellulose nanoparticles. These particles have diameters ranges between 5 and 20 nm and the lengths from 20 nm to 1 micron. Tensile strength and/or modulus of these particles and the abundant availability of their source spurred much interest as replacement of engineered reinforcing fillers [19]. The presence of the hydroxyl groups on the surface of these particles

Sugarcane industries produce large quantities of sugarcane bagasse (i.e., fibrous residue/left over after sugarcane stalks are crushed to extract their juice) annually which in turn is used in the plant for energy co-generation for sugar processing and/or alcohol production [22–26]. Consequently, the black solid waste produced is collected using a bag house filter as a byproduct known as sugarcane bagasse ashes. The collected by-product often consists of fine burnt and coarse unburnt or partially burnt particles. These ashes are non-biodegradable which causes environmental concerns considering their disposal. Some industries adopted

offers the advantage for their functionalization [20, 21].

**Figure 1.** SEM images of (a) uncarbonized and (b) carbonized sugar bagasse [14].

changes in the combustion temperatures as it can be obtained at burning temperatures ranging between 400 and 500°C.

and dispersion of the fibers for highly hydrophobic polymer matrices which causes detrimental

Compression molding was also used to prepare the SB-based composites [36]. This method, however, resulted in blisters, weak interfacial adhesion and inhomogeneous fiber distribution,

Melt extrusion followed by melt compression of SB/HDPE composites was studied by Mulinari et al. [37]. The SB cellulose was extracted using sulfuric acid in a reactor followed by surface

reduced the extent of agglomeration in the composite materials. Moreover, the adhesion between the cellulose and HDPE was improved by surface modification. It was concluded that these processing methods are applicable to produce composites materials using hydrophobic polymers such as HDPE and PP. It worth mentioning that these melt processing methods did not have a significant influence on the extent of the dispersion of the fillers as well as their adhesion. As far as the modification of the filler surface is concerned, it can be concluded that regardless of the type/structure (form) of filler the surface modification can improve the disper-

The addition of the filler into the precursor (polymer monomer) increases the possibility of good dispersion and interaction between the polymer and filler. Motaung et al. [31] prepared CNC/nylon nanocomposites *via in situ* polymerization. The CNC were added into hexamethylenediamine (i.e., nylon monomer) followed by sonication to enhance the dispersion of the CNCs. Nevertheless, the content of the filler played a major role on the dispersion as well as adhesion. Despite the better dispersion obtained under this processing method, for CNCbased composites this scenario can cause a detrimental effect on the resulting properties of the composite materials. The interwhiskers network formed between the nanocrystals is impor-

Sugarcane bagasse is currently used as a one of the sources of the cellulose nanocrystals (CNCs) for the reinforcing polymers. In these studies the state of dispersion of the CNC in water was maintained by adopting the solution casting method [41, 42]. In this method the nanocrystals are mixed with the polymers in a suitable solvent and allow the solvent to evaporate. Uniform distribution of the nanocrystals within the polymeric material was obtained which can lead to other physical and/or chemical properties. It is also essential to take into account the amount of the nanocrystals incorporated into the polymeric material since the higher the content may result in the agglomeration of the nanocrystals which could cause detrimental effect on the intended application or desired properties [42]. Similar preparation method was utilized in the preparation of SB fibers composites especially for polymers which are soluble in water [30].

tant to achieve desired properties in CNC/polymer nanocomposites [39, 40].

kinetic mixer followed by compression molding [17, 38]. The modification using ZrOCl<sup>2</sup>

·8H2

O). In another studies, they used thermo-

Sugarcane Bagasse and Cellulose Polymer Composites http://dx.doi.org/10.5772/intechopen.71497

> ·8H2 O

231

effect on the properties of the resulting composite material [35].

regardless of the fiber retreatment.

modification using zirconium oxychloride (ZrOCl<sup>2</sup>

sion and adhesion for improved properties.

*4.1.2. In situ processing*

*4.1.3. Solution casting*
